Acyclic diene metathesis (ADMET) polymerization is a step polycondensation process that has been used to obtain macromolecules. In ADMET polymerization, a diene is efficiently condensed to an unsaturated polymer by the removal of a small olefin (usually ethylene).
There is provided according to the present invention a polymer having an ethylenically unsaturated backbone repeat unit that includes at least two metal atoms bonded to each other wherein the backbone repeat unit includes only one ethylenically unsaturated functional group or the ethylenically unsaturation is separated by at least one saturated carbon atom from the metal-to-metal atoms. Preferably, the polymer includes a backbone repeat unit having the formula:
xe2x80x94C(R3)xe2x95x90C(R3)xe2x80x94[C(R3)(R4)]nxe2x80x94[M(R1)(R2)]axe2x80x94[C(R3)(R4)]pxe2x80x94
wherein n is 0 to 4 or 0 to 50, preferably 2 to 50; a is at least 2; p is 0 to 4 or 0 to 50, preferably 2 to 50; R1 and R2 are each independently selected from hydrogen, halogen, lower alkyl having 4 or fewer carbon atoms, alkenyl having 4 or fewer carbon atoms, or aromatic having one ring; R3 and R4 are each independently selected from hydrogen and lower alkyl having 1 to 4 carbon atoms; and M is a metal atom selected from at least one of Sn, Ge, Pb, Hg, Ni, Pd, Pt, Cr, Fe, Co, Cu and Zn.
The present invention also provides a method for making an ethylenically unsaturated polymer that includes at least two metal atoms bonded to each other comprising reacting a diene monomer that includes a polymetallane segment in the presence of an effective catalyst to obtain the polymer.
In particular, the polymers of the invention (III) are synthesized via acyclic diene metathesis (ADMET) polymerization of telechelic polymetallane dienes (I) catalyzed by olefin metathesis catalysts based on organometallic complexes of transition metals such as Mo, W, Ta, Ti, Ru (II), Re, Os or Nb. 
There are numerous known metathesis catalysts that might be useful in the invention. Transition metal carbene catalysts are well known. Illustrative metathesis catalyst systems include rhenium compounds (such as Re2O7/Al2O3, ReCl5/Al2O3, Re2O7/Sn(CH3)4, and CH3ReO3/Al2O3xe2x80x94SiO2); ruthenium compounds (such as RuCl3, RuCl3(hydrate), K2[RuCl5xe2x80x94H2O], [Ru(H2O)6](tos)3 (xe2x80x9ctosxe2x80x9d signifies tosylate), ruthenium/olefin systems (meaning a solution or dispersion of preformed complex between Ru and olefin (monomer) that also includes a xcex2-oxygen in the presence or absence of a soluble or dispersed polymer where the polymer can be an oligomer or higher molecular weight polymer prepared by metathesis or other conventional polymerization synthesis), and ruthenium carbene complexes as described in detail below); osmium compounds (such as OsCl3, OsCl3(hydrate) and osmium carbene complexes as described in detail below); molybdenum compounds (such as molybdenum carbene complexes (such as t-butoxy and hexafluoro-t-butoxy systems), molybdenum pentachloride, molybdenum oxytrichloride, tridodecylammonium molybdate, methyltricaprylammonium molybdate, tri(tridecyl)ammonium molybdate, and trioctylammonium molybdate); tungsten compounds (such as tungsten carbene complexes (such as t-butoxy and hexafluoro-t-butoxy systems), WCl6 (typically with a co-catalyst such as SnR4 (R signifies alkyl) or PbR4), tungsten oxytetrachloride, tungsten oxide tridodecylammonium tungstate, methyltricaprylammonium tungstate, tri(tridecyl)ammonium tungstate, trioctylammonium tungstate, WCl6/CH3CH2OH/CH3CH2AlCl2, WO3/SiO2/Al2O3, WCl6/2,6-C6H5xe2x80x94C6H5OH/SnR4, WCl6/2,6-Brxe2x80x94C6H3OH/SnR4, WOCl4/2,6-C6H5-C6H5OH/SnR4, WOCl4/2,6-Brxe2x80x94C6H3OH/SnR4); TiCl4/aluminum alkyl; NbOx/SiO2/iso-butyl AlCl2; and MgCl2. As indicated above, some of these catalysts, particularly tungsten, require the presence of additional activator or initiator systems such as aluminum, zinc, lead or tin alkyl. Preferred catalysts are ruthenium compounds, molybdenum compounds and osmium compounds.
Telechelic polymetallane dienes (I) may be synthesized using any single or a combination of the following procedures according to the invention:
1) The use of alkenyl metallanes (IV) as chain limiters in the dehydrogenation of metal dihydrides (V) catalyzed by organometallic complexes of transition metals such as Zr, Ti, Rh, Pt, Pd, Ni, V, Hf, Sc or Ta (VI). 
2) The use of alkenyl metal halides (VII) as chain limiters in the Wurtz-type coupling of metal dihalides (VIII) in the presence of alkali metals such as Li, Na, K, Rb or Cs (IX). 
3) The sequential alkenylation of polymetallane dihalides (XI) by organometallic reagents bearing the alkenyl moiety (X) (w and y are independently any number between 2 and 50). 
4) The coupling of alkenyl metallanes (IV) with metal diamides (XII). 
In all schemes:
M is a metal atom selected from at least one of Sn, Ge, Pb, Hg, Ni, Pd, Pt, Cr, Fe, Co, Cu and Zn;
R1 and R2 are independently hydrogen, alkyl or aryl groups containing 2 to 50 carbons;
w and y are independently any number between 2 and 50;
x and n are independently any number larger than 1;
X is a halogen atom such as Cl, Br or I;
E is any electrophile consisting of or containing metals such as Li, Na, K, Cs, Mg, Zn, Cd or Hg.
In each of these schemes it is possible to use a mixture of reactants that could have different divalent radicals ( )w and ( )y wherein the number of carbon atoms varies. In addition, R1 and R2 could be bonded to form a cyclic structure to the same metal atom or to adjacent metal atoms.
Another possible synthetic route to suitable polymetallane monomers is to use cyclopolymetallane reactants and (1) subject them to UV radiation, (2) two step reaction with CH2xe2x95x90CH(CH2)nE and then CH2xe2x95x90CH(CH2)nX (wherein n, E and X are the same as identified above), and (3) reacting with CH2xe2x95x90CH(CH2)nM(X)2(CH2)nCHxe2x95x90CH2.
The polymer should have a high amount of metal, at least about 20 weight %, preferably at least about 50 weight %, based on the weight of the polymer. Polymers with such a structure should have very advantageous electrical and thermal conductivity properties and thus can be used in conductive films, fibers and solders and photoresists. In addition, they should be malleable and easy-to-process since they are very soluble in organic solvents and should have good melt processing characteristics.
The first step in our approach to ADMET polymers containing polymetallane segments consists of the design and synthesis of suitable diene monomers containing at least one metalxe2x80x94metal "sgr" bond. In order to determine the compatibility between this functionality and the metathesis catalysts employed in the polymerization, we have concentrated our efforts on the preparation of di- and tristannane dienes. The alkenylation of a tri- or distannane dichloride appeared attractive to us since a variety of carbonated segments can be introduced by the choice of the alkenylating group.
The synthesis of monomer of formula 2 as shown in Scheme 1 below involves the in situ generation of Bu2SnHCl, its dehydrogenative coupling to the distannane dichloride, and the subsequent reaction of this dichloride with a nucleophilic alkenyl group, and we have attempted to reduce this procedure to a one-pot synthesis scheme based on the difficulties often associated with the purification of tin halides.
The room temperature disproportionation of equimolar amounts of Bu2SnCl2 and Bu2SnH2 leading to Bu2SnHCl has been previously reported in Newmann, W. P.; Pedain, J. Tetrahedron 1964, 36, 2461; (b) Kawakami, T.; Suimoto, T.; Shibata, I.; Baba, A.; Matsuda, H.; Sonoda, N. J. Org. Chem. 60, 2677 (1995). The equilibrium concentrations are reached in ca. 10 min at 25xc2x0 C. Addition of a catalytic amount of dry pyridine or a Pd complex to this mixture has also been reported in Newmann et al. to cause the quantitative decomposition of the Bu2SnHCl to the distannane dichloride. The palladium catalyzed coupling appears to be the most efficient, and Bu4SN2CL2 solutions are obtained afterxe2x80x94often vigorousxe2x80x94hydrogen evolution from the precursor Bu2SnHCl solutions. This disappearance of the signal centered at 44.6 ppm and the simultaneous appearance of a new sharp singlet at 109.0 ppm in the (proton decoupled) 119Sn-NMR (1J119Snxe2x88x92119Sn=2420 Hz), have proven to be very useful in the monitoring of this reaction. We have also observed that this methodology can be extended to other polystannane dichlorides, which can be used as precursors for diene monomers.
The alkenylation of the distannane dichloride is a facile reaction. Gentle reflux of the dichloride with the Grignard reagent generated from 5-bromo-1-pentene affords after workup a mixture of the dienes of formulae 2, 3, and 4 identified by their distinct resonances in the 119Sn-NMR. However, we have been unable to produce 2 free of other dienes, and attempts to separate these dienes have also proven unsuccessful. Bu2SnCl2 remaining from the incomplete disproportionation reaction accounts for the presence of formula 3, while the coupling of remaining Bu2SnH2 with Bu2SnHCl in the second step explains the presence of diene of formula 4. To our surprise, these compounds are quite stable not only to aqueous workup of the Grignard reaction, but also to adsorbents such as silica gel, which allows their isolation in adequate purity for ADMET polymerization.
Upon exposure to the molybdenum catalyst 1, this purified diene mixture produced the ADMET terpolymer of formula 6 in almost quantitative yield. (see Scheme 2 below) Ethylene evolution is very vigorous during the first 4 h of the reaction, and the viscosity of the reaction mixture increases steadily suggesting polymerization. After this time, ethylene bubbling rate decreases, but continues throughout the reaction until viscosity prevents magnetic stirring. Characterization of the crude polymer sample reveals that polymerization has indeed taken place, along with the incorporation of the three stannadienes 2, 3 and 4. Both 13C and 1H-NMR of the polymer show the conversion from terminal dienes to internal olefins. New signals at 5.5-5.6 ppm (1H), and at 131.2 and 130.6 ppm (13C) account for the new olefin linkages, in both cis and trans isomeric forms. Polymerization is also evident by the splitting of the 119Sn signals originally present in the monomer mixture, due to the slightly different magnetic environments caused by the olefin linkages.
Precipitation of the polymers from CDCl3 or C6D6 solutions into methanol yields the polymers as viscous liquid samples. End group analysis based on NMR Spectroscopy suggests an average degree of polymerization of 20. (Calculated Mn=11,000 g/mol).